The bizarre all-Democratic runoff for a state Senate seat long held by Republicans would never have happened under legislation set to be introduced before next year’s legislative session.

State Sen. Josh McKoon, a Republican candidate for secretary of state, said he’ll pre-file legislation next week that would require both parties to nominate their own candidates in a special election.

It was spurred by the surprising results in Tuesday’s vote to replace Republican Hunter Hill, who vacated the Atlanta-based seat to run for governor. The district was becoming increasingly competitive – Hill only narrowly carried it last year – but few predicted the two top finishers would be Democrats.

That’s exactly what happened with a field of five Republicans splitting the GOP vote, while the two leading Democrats – Jaha Howard and Jen Jordan – carved up the Democratic support. That helped them finish atop the field, even though Republicans narrowly outvoted Democrats overall.

McKoon’s measure would establish party primaries in special elections rather than the wide-open races that state law now requires. He called Tuesday’s results “an injustice to the citizens of this state to be denied fair representation.”

Democrats were quick to criticize McKoon’s proposal as an attempt to circumvent his party’s defeat at the polls. Senate Minority Leader Steve Henson questioned why McKoon wasn’t as “indignant” in 2012 when the district’s lines were redrawn to boost its conservative vote.

“With this seat, Democrats have 34 percent of the seats in the Senate. No one argues that at least 45 percent of the Georgia vote is Democratic,” said Henson, D-Tucker. “So it’s obvious Josh is not spending his time worrying about fairness.”

McKoon’s push was seconded by Cobb County GOP chair Jason Shepherd, who criticized Republican Michael Williams for blaming Hill for the defeat and lamented a “process where a majority Republican district can end up with two Democrats in the runoff.”

“It’s time for the Legislature to fix the process once and for all before more Republican districts flip because of a process that doesn’t reflect the will of the voters,” he said.